Traumatic brain injury (TBI) has been associated with dementia, but the association has not been studied over a long period of time. Anna Nordström and Peter Nordström from Umeå University in Sweden recently published a study in PLOS Medicine that investigates this gap in knowledge.

In the new study, the researchers tracked all diagnoses of dementia and TBI in Swedish nationwide databases from 1964 through 2012. They used the data to make comparisons within three groups of patients. In one group, 164,334 people with TBI were compared with control participants who did not have TBI. In the second group, 136,233 people with TBI who were later diagnosed with dementia were compared with control participants who did not develop dementia, and in a third group, the researchers studied 46,970 sibling pairs with one sibling having a TBI.

The researchers found that in the first year after TBI, the risk of dementia increased by four- to sixfold. Thereafter, the risk decreased rapidly but was still significant more than 30 years after the TBI.

“The results indicate that a TBI could increase the risk for dementia even more than 30 years after the incident,” the authors say. “To our knowledge, no previous prospective study with similar power and follow-up time has been reported.”

While their results do not definitively show that TBI causes increased dementia risk, the researchers hope to further explore whether the associations found in this study are causal in future research.

Author

Tessa Gregory

Tessa is the Journal Media Manager at PLOS. She graduated from the University of California, Berkeley with degrees in Rhetoric and Music. She can be reached by email at tgregory@plos.org and on Twitter at @tessagregs.